1. Field of the Invention
The present invention relates to a stereoscopic microscope for magnifying an object, and more particularly, to a stereoscopic microscope in which an image of the object is electronically taken by an image taking device such as a CCD.
2. Description of the Related Art
A stereoscopic microscope is used as a surgical microscope for magnifying minute tissues such as brain cells during surgery.
Since it is difficult to distinguish minute tissues of an intricate organ such as a brain by the naked eye, the surgical microscope is required to proceed surgery on such an organ. Besides, since it is impossible to observe the three-dimensional structure of a tissue with a monocular microscope, a stereoscopic microscope has been used to enable three-dimensional magnifying observation of the tissue in order to perform accurate operations.
However, with the conventional optical stereoscopic microscope, although a lead surgeon or his/her assistant can observe the microscopic image, other staffs such as anesthetists, nurses, interns, and advisers who works at some remote locations cannot observe the same microscopic image. Therefore, they could not pursue their share of tasks with sufficient accuracy and promptness. Similarly, the adviser could not provide timely and proper advice from the remote locations.
It is therefore an object of the present invention to provide a stereoscopic microscope, which enable the stuffs other than the lead surgeon to observe magnified stereoscopic images.
For the above object, according to the present invention, there is provided an improved stereoscopic microscope, which includes:
a common close-up optical system that faces an object, the close-up optical system having a single optical axis;
a pair of zoom optical systems that take object light rays passing through the different regions of the close-up optical system, respectively, to form a pair of primary images, the optical axes of the zoom optical systems being parallel to the optical axis of the close-up optical system;
a pair of field stops that are arranged at the positions of the primary images;
a pair of relay optical systems that relay the primary images to form a pair of secondary images;
an inter-axis distance reducing element that brings the object light rays from the relay optical systems close to each other;
an image taking device that captures the secondary images formed on an image taking surface thereof; and
an illuminating optical system that guides illumination light emitted from a light source to illuminate the object.
With this construction, the object light rays incident on the close-up optical system form the primary images having predetermined parallax at the field stops through the zoom optical systems. The close-up optical system is adjusted so that the front focal point thereof coincides with the object. Thus, the close-up optical system has a function of a collimator lens that converts the divergent light rays from the object into the parallel light rays. The primary images are transmitted by the relay optical systems. The inter-axis distance reducing element reduces the inter-axis distance of the right and left light rays. The primary images are re-imaged by the relay optical systems as the secondary images on the adjacent regions on the single image taking surface of the image taking device, respectively. The captured images are displayed on a display device such as an LCD panel or a CRT. The lead surgeon and the other stuffs can observe the magnified stereoscopic images on the display devices through stereoscopic viewers.
For taking color images, the image taking device may adopt a single color CCD or may adopt a combination of a plurality of CCDs and chromatic beamsplitters. When a plurality of CCDs are used, the right and left images are formed on the adjacent regions of the respective CCD.
The diameter of the close-up optical system is preferably set to be larger than the diameter of a circle that includes the maximum effective diameters of the zoom optical systems and the maximum effective diameter of the illuminating optical system. Further, each lens of the close-up optical system may have a semicircular shape in which one side is cut out. In such a case, the illuminating optical system may be arranged in the cutout space of the close-up optical system.
Still further, the close-up optical system preferably includes a first lens group of a negative refractive power and a second lens group of a positive refractive power arranged in that order from the object side. In such a case, the second lens group may be movable along the optical axis direction for focusing according to the object distance.
The close-up optical system preferably satisfies the following condition (1) in order to reduce spherical aberration.
fA greater than 500xe2x80x83xe2x80x83(1)
where fA is a focal length (unit: mm) of the close-up optical system. When the focal length of the close-up optical system is variable, the focal length fA is defined as the longest focal length.
A plane that includes optical axes of the zoom optical systems is preferably offset in parallel from a meridional plane of the close-up optical system. Further, it is preferable that each of the zoom lens systems includes first, second, third and fourth lens groups of positive, negative, negative and positive refractive powers, respectively, in that order from the side of the close-up optical system. In such a case, the second and third lens groups move for zooming along the optical axis direction while keeping the first and fourth lens groups at constant positions.
Each of the relay optical systems may include first, second and third lens groups of positive refractive powers, respectively. The first and second lens groups collimate the divergent light passing through the field stops in combination and the third lens group converges the parallel light rays exited from the second lens group. Furthermore, an aperture stop may be located between the second lens group and the third lens group of the relay optical system.
The relay optical systems preferably satisfy the following condition (2) in order to reduce the total size and weight of the microscope.
xe2x88x923 less than MR less than xe2x88x921xe2x80x83xe2x80x83(2)
where MR is imaging magnification of the relay optical systems.
The inter-axis reducing optical element may include a pair of optical axis shifting prisms (offset prisms). In such a case, each of the optical axis shifting prisms being provided with incident and exit surfaces that are parallel to each other and first and second internal reflecting surfaces that are parallel to each other.
The illuminating optical system is preferably provided with an illumination lens for projecting the illumination light emitted from the light source and a wedge prism for deflecting the illumination light to coincide the illuminating region with the image taking region.